Delayed and current stimulus control in successive discriminations.
A brief neutral stimulus between components scrubs carry-over control and sharpens the next discrimination.
01Research in Context
What this study did
The team ran a red-green hue discrimination in a successive schedule. After each color switch, a brief white light came on before the next color.
They wanted to know if this neutral white gap would cut carry-over control from the prior color.
What they found
Without the white gap, birds responded to the new color as if the old one still mattered. Accuracy dipped at the start of each component.
Adding the white gap wiped out most of that dip. The new color gained faster control.
How this fits with other research
Zeiler (1968) saw the same dip in size discriminations and blamed recent reinforcement, not the switch itself. White (1990) shows the switch cue can be the culprit if you give it room to work.
Zentall et al. (1975) found that mixing features at the same time blurs control. White (1990) shows that separating events in time with a neutral cue sharpens it.
Snapper et al. (1969) proved color can dominate form. White (1990) adds that the moment of color change can dominate even the color now on the key unless you insert a buffer.
Why it matters
If you run alternating tasks or mixed VB programs, a quick neutral transition—like a brief ‘ready’ signal—can keep old stimuli from bleeding into the new trial. Try flashing the key white for one second before the next SD. You should see cleaner discrimination at the first response.
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02At a glance
03Original abstract
In a successive discrimination in which successively alternating red and green hues signaled component variable-interval schedules, sensitivity of the ratio of responses in the two components to variation in the component reinforcer ratio decreased systematically during the course of the component. This decrease in stimulus control or discrimination over the course of the component was shown to be the result of delayed control of responding during the component by the stimulus transition between components. When the red-green stimulus transition was altered by interpolating a white stimulus at the end of each 60-s component, discrimination at the beginning of the component (measured by the power-function exponent for sensitivity to reinforcement) was reduced. Conditions with the white stimulus inserted in other quarters of the component indicated that the current discriminative stimulus exerts control over responding throughout the component, whereas during about the first half of the component, response differentials are influenced by the transition between discriminative stimuli.
Journal of the experimental analysis of behavior, 1990 · doi:10.1901/jeab.1990.54-31